As small and medium sized computer systems are becoming less expensive and more powerful, a number of them are being interconnected to form networks to ensure that a number of different types of services are available at any time to users having diverse processing needs, and also to facilitate communications among the various computer system users connected to the network. In many applications, for example, in networked mail applications, it is necessary to send data, in the form of messages, from a user operating one computer on the network, to another user operating another computer, both computers being nodes on the network. A message may contain only a small amount of data, or alternatively, it may contain large amounts, representing data generated by other applications processed by each computer.